Recovery of Iron, Silver and Lead from Zinc Ferrite Residue

The present article aims to develop a technological scheme for processing zinc ferrite residue, which typically forms during the leaching of zinc calcine. This semi-product is currently processed through the Waelz process, the main disadvantage of which is the loss of precious metals with the Waelz clinker. The experimental results of numerous experiments and analyses have verified a technological scheme including the following operations: sulfuric acid leaching of zinc ferrite residue under atmospheric conditions; autoclave purification of the resulting productive solution to obtain hematite; chloride leaching of lead and silver from the insoluble residue, which was produced in the initial operation; and cementation with zinc powder of lead and silver from the chloride solution. Utilizing such an advanced methodology, the zinc leaching degree is 98.30 % at a sulfuric acid concentration of 200 g/L, with a solid-to-liquid ratio of 1:10 and a temperature of 90 °C. Under these conditions, 96.40 % Cu and 92.72 % Fe go into solution. Trivalent iron in the presence of nuclei at a temperature of 200 °C precipitates as hematite. In chloride extraction with 250 g/L NaCl, 1M HCl and a temperature of 60 °C, the leaching degree of lead is 96.79 %, while that of silver is 84.55 %. In the process of cementation with zinc powder, the degree of extraction of lead and silver in the cement precipitate is 98.72 % and 97.27 %, respectively. When implementing this scheme, approximately 15 % of the insoluble residue remains, containing 1.6 % Pb and 0.017 % Ag.